Wide use of mobile devices, such as video cameras, mobile phones, or portable PCs, increases adoption of secondary batteries as a driving power source. Due to high energy density per unit weight and quick recharging capability, lithium-based secondary batteries draw much attention compared to other types including existing Pb batteries, Ni—Ca batteries, Ni—H batteries, or Ni—Zn batteries.
Unlike primary batteries without recharging capability, secondary batteries can be recharged or discharged. In expectancy of various applications, a lot of research efforts have been dedicated to the secondary batteries. Among others, lithium-based secondary batteries exhibit higher operating voltage and per-unit energy density.
Such lithium-based secondary batteries can be classified into lithium ion batteries and lithium ion polymer batteries. The former type adopts liquid electrolyte, and the latter adopts solid polymer electrolyte. Depending on the type of solid polymer electrolyte, the lithium ion polymer batteries can be separated into a full solid type with no electrolyte liquid and a gel polymer type with slight liquid electrolyte.
Subjected to overvoltage or overcurrent state, the secondary batteries cannot guarantee stability, and various efforts are thus attempted to sense and protect such negative situation.
Korean Patent Application Publication No. 2005-72276 discloses a “overvoltage and overcurrent preventing circuit for terminals” which shields overcurrent by a diode and a comparison circuit.
Korean Patent Application Publication No. 2011-54965 discloses a “one-chip battery protecting apparatus” which uses an LDMOS (Laterally Diffused Metal Oxide Semiconductor) to implement a power-off circuit.
In general, secondary batteries used for electric vehicles need to provide a high current ranging from 100 A to 300 A. Accordingly, there is a need for preventing a high-capability secondary battery from being damaged due to overcurrent.